Two 了s

Hiya I posted this in a lesson conversation, but it didn't get picked up by staff. I found the sentence 我忘了买肉了 - wǒ wàng le mǎi ròu le - "I forgot to buy meat". Why are there two 了 in this sentence? Would 我忘了买肉 not suffice? or 我忘买肉了? Could someone explain?